Methods for protein purification

ABSTRACT

The present invention relates to a recombinant construct comprising a nucleotide sequence encoding a fusion protein comprising a soluble form of human SSAO (Semicarbazide-Sensitive Amine Oxidase), a secretable fusion partner, a signal peptide; and a protease cleavage site. The said construct is useful in methods for purification of a soluble form of human SSAO.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority from Swedish Patent Application No, 0100625-3, filed Feb. 23, 2001, and U.S. Provisional Patent Application Serial No. 60/272,247, filed Feb. 28, 2001. These applications are incorporated herein by reference in their entirety.

TECHNICAL FIELD

[0002] The present invention relates to a recombinant construct comprising a nucleotide sequence encoding a fusion protein comprising a soluble form of human semicarbazide-sensitive amine oxidase (SSAO), a secretable fusion partner, a signal peptide, and a protease cleavage site. The invention also relates to methods for purification of a soluble form of human SSAO, said methods utilizing the recombinant construct.

BACKGROUND ART

[0003] Semicarbazide-sensitive amine oxidase (SSAOs) belong to the copper-containing amine oxidase family of enzymes (CuAO; EC. 1.4.3.6) and are widely distributed among both eukaryotic and prokaryotic organisms (Buffoni, 1993). The physiological role of this abundant enzyme is essentially unknown and endogenous substrates with high affinity have so far not been identified, although benzylamine is an artificial high-affinity substrate (Buffoni, 1993; Callingham et al., 1995; Lyles, 1996, Hartmann and McIntire, 1997; Holt et al., 1998). In humans high SSAO activity is found in vascular smooth muscle cells (Lewinsohn 1984; Nakos and Gossrau, 1994; Yu et al., 1994; Lyles and Pino, 1998; Jaakkola et al., 1999). SSAO activity has also been detected in smooth muscle cells of non-vascular type and in endothelial cells (Lewinsohn, 1984; Castillo et al., 1998; Jaakkola et al., 1999). Small amounts of SSAO protein is also found in blood showing similar properties compared to the tissue-bound form (Yu and Zuo, 1993; Yu et al., 1994; Kurkijärvi et al., 1998).

[0004] Many studies have demonstrated that SSAO activity in blood plasma is elevated in several human conditions such as heart failure, atherosclerosis and diabetes (Lewinsohn, 1984; Boomsma et al., 1997; Ekblom, 1 p98; Boomsma et al., 1999; Meszaros et al., 1999). The mechanism(s) underlying these alterations of enzyme activity are currently uncharacterized. It has been suggested that reactive aldehydes and hydrogen peroxide produced by endogenous amine oxidases could be causative or contribute to the progression of cardiovascular diseases, and that inhibition of SSAO activity in diabetics might decrease vascular complications (Ekblom, 1998).

[0005] Recently it was found that the cDNA sequence of human SSAO (Zhang and McIntire, 1996) is identical to the vascular adhesion protein 1 (VAP-1), which participates in lymphocyte recirculation by mediating the binding of lymphocytes to peripheral lymph node vascular endothelial cells (Smith et al., 1998; see also WO 98/53049). The cDNA sequence of SSAO/VAP-1 is deposited under GenBank Accession Nos. U39447 and NM_(—)003734 (SEQ ID NO: 1). VAP-1 has also been found to be up-regulated on the endothelial cell surface under inflammatory conditions (Smith et al., 1998). However, the adhesive properties of SSAO have only been found in endothelial cells. In smooth muscle cells, SSAO does not support binding of lymphocytes (Jaakola et al., 1999). DNA-sequence analysis, structural modeling and experimental data suggest that human SSAO is a homodimeric glycoprotein consisting of two 90-100 kDa subunits anchored to the plasma membrane by a single N-terminal membrane spanning domain (Morris et al., 1997; Smith et al., 1998; Salminen et al., 1998).

[0006] No reports have so far been published regarding the purification of a recombinant mammalian SSAO or purification to near homogeneity of larger amounts of a human SSAO from a natural source. One report has described the use of a FLAG peptide fused to the N-terminal end of full-length human SSAO for detection purposes, but no results were presented regarding its use for purification of the human SSAO protein (Smith et al., 1998). Monoclonal antibodies have been used to immunoaffinity purify small amounts of human SSAO from serum and tissue homogenates for immunoblotting (Smith et al., 1998; Kurkijärvi et al., 1998). Consequently, there is a need for alternative methods for the purification of human SSAO in significant amounts.

[0007] Glutathione S-transferase (GST) from Schistosoma japonicum is a homodimeric cytoplasmic enzyme that can be purified by affinity chromatography using immobilized cofactor glutathione, followed by competitive elution using reduced glutathione (GSH). Taking advantage of this specific interaction, a gene fusion system for E. coli intracellular expression was developed by Smith and co-workers (Smith & Johnson, 1988; see also WO 88/09372) to facilitate detection and purification of recombinant proteins fused to GST. A potential drawback with using GST as fusion partner is the possibility that the free cysteines on its surface can crosslink with free cysteines on e.g. the fused target protein when exposed to an oxidizing environment. To minimize this risk and to allow for secretion of GST-fusion proteins a mutant form of GST was recently developed, which retain both its ability to form homo-dimers and its enzyme activity (Tudyka and Skerra, 1997). The homo-dimerization propensity of GST can be used to provoke dimerization of the fused target protein e.g. for the purpose of increased avidity effects (Tudyka and Skerra, 1997).

[0008] Alternative homodimeric fusion partners described in the literature are e.g. the Fc region of immunoglobulins (Hollenbaugh et al., 1992; Sakurai et al., 1998; Lo et al., 1998; Dwyer et al., 1999) and leucine zippers such as GCN4 (Rieker and Hu, 2000; Müller et al., 2000). Several different proteins have been fused to these homodimeric protein domains for different purposes e.g. to increase avidity (Dwyer et al., 1999; Muller et al., 2000) and to restore high-affinity DNA binding of truncated DNA-binding proteins (Rieker and Hu, 2000). Fc-fusion protein can be purified by protein A-affinity chromatography involving elution with low pH buffers (Sakurai et al., 1998; Lo et al., 1998), which may decrease activity of the fused target protein (Gräslund et al., 1997). Another problem associated with using Fc as fusion partner is the use of serum for cell growth, which complicate detection and purification of secreted Fc-fusions since serum contains large amounts of immunoglobulins (Sakurai et al., 1998). The leucine zipper GCN4 has mostly been used as fusion partner for proteins expressed in E. coli (Miller et al., 2000) and an affinity-tag might has to be fused to facilitate purification.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009]FIG. 1 is a schematic illustration of a GST-SSAO DNA construct (SEQ ID NO: 19) encoding a fusion protein (SEQ ID NO: 20). The three cysteine to serine mutations (residues 85, 138, and 178 according to the sequence having GenBank™ Accession No. M 14654) in the GST fusion partner are shown with boldface letters. Boxed sequence represents the recognition sequence for the 3C-protease.

[0010]FIG. 2 is an overview of an SSAO purification process. The determined specific activities for each purification step are indicated.

[0011]FIG. 3 is a schematic illustration of the GST-SSAO expression vector designated pMB887.

DISCLOSURE OF THE INVENTION

[0012] According to the present invention, it has unexpectedly been found that soluble human SSAO can be produced in milligram quantities in a purification system utilizing a fusion partner capable of enabling dimerization of soluble SSAO. Consequently, in a first aspect this invention provides a recombinant construct comprising a nucleotide sequence encoding a fusion protein comprising:

[0013] (i) a soluble form of human SSAO;

[0014] (ii) a secretable fusion partner enabling dimerization of SSAO;

[0015] (iii) a signal peptide allowing for secretion of a polypeptide from a host cell into the culture medium; and

[0016] (iv) a protease cleavage site located between the human SSAO variant and the fusion partner.

[0017] As will be understood by the skilled person, the recombinant construct can optionally comprise one or more nucleotide sequences coding for spacer amino acid sequences of various lengths. Such spacer sequences could be used in order to increase the flexibility within the fusion protein, or to increase the space between protein domains so that folding can take place independently of adjacent domains. Further, spacers could be useful for increasing the accessibility for a protease to cleave at an introduced cleavage recognition sequence.

[0018] The soluble form of human SSAO is preferably lacking the membrane spanning portion of wild-type human SSAO. The membrane spanning portion of the SSAO polypeptide is known in the art (Morris et al., 1997; Holt et al., 1998; Smith et al., 1998) and is essentially set forth as amino acids 5 to 27, in particular amino acids 6 to 26, of SEQ ID NO: 2.

[0019] The amino acid sequence for human SSAO, excluding the membrane spanning portion, preferably comprises, or essentially consists of, positions 29 to 763 in SEQ ID NO: 2. However, the skilled person will understand that a part of the membrane-spanning portion could be included in the SSAO polypeptide while the polypeptide would still retain its essentially soluble properties. Consequently, the amino acid sequence for human SSAO could comprise e.g. positions 27 to 763, or 28 to 763, of SEQ ID NO: 2, including fragments thereof having substantially the biological activities of human SSAO. Further, the term “human SSAO polypeptide” is intended to encompass mutants and naturally occurring variants of human SSAO, either having retained enzymatic activity or protein interaction (e.g. adhesion function), or designed to facilitate structural studies (e.g. improved properties for crystallization), or mutated to facilitate studies of structure/function relationships (which also includes inactive mutants).

[0020] The fusion partner can be fused to the C-terminal or N-terminal portion of the human SSAO polypeptide. It is envisaged that the fusion protein could comprise more than one fusion partner, for instance one fused to the N-terminal and one fused to the C-terminal part of SSAO. An additional fusion partner could be an additional affinity tag, or a reporter protein such as Enhanced Green Fluorescent Protein (EGFP).

[0021] A large number of different gene fusion systems and fusion partners have been described. In such systems, different types of interactions, such as enzyme-substrate, bacterial receptor-serum protein, polyhistidines-metal ion, and antibody-antigen, have been utilized (Uhlén et al., 1992). Various gene fusion systems for affinity purification are also known in the art. Examples of fusion partners used in such systems (for reviews, see e.g. Nilsson et al., 1997; or Sheibani, 1999) comprise staphylococcal Protein A and its derivative Z; the albumin-binding protein from streptococcal Protein G; glutathione S-transferase (GST); polyhistidine tags; biotinylated affinity tags (e.g Biotin AviTag); E. coli maltose-binding protein; cellulose binding domains; the FLAG peptide; and Strep-tag. Alternative systems may be engineered using protein scaffolds for generation of novel ligand receptors (see Skerra, 2000, and references therein). These novel binding proteins, e.g. affibodies, may then be useful as fusion partners for different applications (Nygren and Uhlén, 1997; Nord et al., 1997).

[0022] According to this invention, the said fusion partner should enable dimerization of SSAO. A suitable fusion partner is glutathione S-transferase (GST), because of its propensity to dimerize and because the purification procedure has the potential to be performed under mild conditions using chromatography media with immobilized glutathione (e.g. from Amersham Pharmacia Biotech, Uppsala, Sweden). In addition, GST can conveniently be detected either by its enzymatic activity or by the use of GST specific antibodies or glutathione, using commercially available GST detection systems (e.g. from Amersham Pharmacia Biotech). The fusion partner could also be a functionally equivalent variant of GST, having retained propensity for dimerization and having binding properties allowing affinity purification. The said fusion partner is more preferably a variant of S. japonicum GST (GenBank Accession No. M14654; SEQ ID NOS: 3 and 4), designed for secretion out of the host cell, having one or more of the cysteine residues in positions 85, 138, and 178 replaced with other amino acid residue(s). Most preferably, the said variant has all the cysteine residues in positions 85, 138, and 178 replaced with serine residues (see Tudyka & Skerra, 1997 and SEQ ID NO: 5).

[0023] In addition, the said recombinant construct should comprise a nucleotide sequence encoding an N-terminal signal peptide, which allows for secretion of the said fusion protein from a host cell into the culture medium. For production of a human protein such as SSAO in a eukaryotic cell a homologous signal peptide is preferred. For production of SSAO in HEK293 cells e.g. a mouse IgG1 heavy chain signal peptide (Kabat et al., 1991) may be used. Other suitable signal peptides are known in the art and are described in e.g. Kabat et al., supra.

[0024] Several methods have been described for site-specific cleavage of fusion proteins based on treatment with chemical agents such as CNBr or hydroxylamine, or enzymes such as enterokinases, Factor Xa, thrombin, subtilisin or other proteases (see e.g. Nilsson et al. (1997) and references therein). According to this invention, the said fusion partner can conveniently be removed from human SSAO by protease cleavage. The protease to be used for cleavage can e.g. be a 3C protease from the picornavirus family, e.g. a rhinovirus or enterovirus 3C protease (Walker et al., 1994). Consequently, the protease cleavage site can preferably be a cleavage site for a 3C-protease from the picornavirus family, e.g. a rhinovirus or enterovirus 3C protease. In one exemplified form of the invention, the said 3C protease cleavage site comprises the amino acid sequence EALFQG (SEQ ID NO: 6). However, the skilled person will be able to identify other suitable cleavage sites, see e.g. Blom et al. (1996) and references therein.

[0025] The recombinant construct according to the invention could e.g. comprise a nucleotide sequence encoding essentially the amino acid sequence shown in FIG. 1. The invention also provides an expression vector, prepared according to standard methods, comprising the recombinant construct according to the invention. Such an expression vector is exemplified by the expression vector termed pMB887, shown in FIG. 3.

[0026] In another aspect, the invention provides a method for the purification of a recombinant human SSAO polypeptide comprising the steps of:

[0027] (i) transfecting cells with an expression vector according to the invention, as defined above;

[0028] (ii) culturing the said cells under conditions allowing for the fusion protein expressed by the vector to be secreted into the cell medium;

[0029] (iii) binding the obtained fusion protein to a medium comprising a ligand having affinity for the fusion partner;

[0030] (iv) separating the said fusion partner and the SSAO polypeptide; and

[0031] (v) recovering the purified human SSAO polypeptide.

[0032] The fusion partner can be separated from the human SSAO variant either when the fusion protein is still attached to the affinity ligand, or when the fusion protein has been released from the affinity ligand. When the said fusion partner is GST, the said ligand having affinity for the fusion partner is preferably glutathione, or a derivative thereof. Alternatively, antibodies directed to GST could be used as affinity ligands.

[0033] As mentioned above, the fusion partner can be separated from human SSAO by protease cleavage with e.g. a picornavirus, such as rhinovirus, 3C-protease. The said protease can be fused to a fusion partner, thereby obtaining a “fusion protease” (see Walker et al., 1994; Gräslund et al., 1997). Such a fusion partner can conveniently be the same fusion partner as used for the SSAO polypeptide, e.g. glutathione S-transferase. However, other suitable fusion partners for proteases, such as albumin-binding protein from streptococcal Protein G, are known in the art, see e.g. Gräslund et al., 1997. The said fusion protease can be separated from the SSAO polypeptide by a process comprising binding the fusion protease to a medium comprising a ligand having affinity for the said fusion partner. Consequently, when the fusion partner is GST, the said ligand is preferably glutathione, or a derivative thereof. As mentioned above, antibodies directed to the fusion partner could also be used as affinity ligands. A commercially available system is the PreScission Protease (Amersham Pharmacia Biotech,) which is a genetically engineered fusion protein consisting of S. japonicum GST and human rhinovirus 3C protease.

[0034] For certain application, it might be advantageous to have SSAO immobilized. This may be achieved e.g. by an affinity-tag such as GST as described above. Examples of applications where a fusion protein is immobilized via an affinity-tag include: capture of protein ligands, analysis of protein-protein interactions, and use in bioreactors (Nilsson et al., 1996; Nord et al., 1997; Shpigel et al., 1999). However, many alternative methods for protein immobilization are described (see e.g. Tischer and Kasche, 1999, and references therein), that also may be applicable for immobilization of GST-SSAO or SSAO after removal of the fusion partner, such as covalent binding and non-covalent adsorption. In addition, the SSAO protein might also be encapsulated in e.g. sol-gel or an artificial cell e.g. a liposome (see e.g. Liang et al., 2000, and references therein).

[0035] One advantage with an affinity-tag such as GST is that an oriented immobilization can be achieved, often in a one-step procedure directly from e.g. a cell lysate (Nilsson et al., 1997; Saleemuddin, 1999). This may result in good steric accessibility of active binding sites and increased stability (Saleemuddin, 1999; Turkova, 1999). Examples of alternative affinity-tag approaches that has been used for immobilization of proteins are e.g. peptides and proteins that can be specifically biotinylated by biotin ligase and used as fusion partners to take advantage of the very strong interaction (K_(d)˜10⁻¹⁵) between biotin and streptavidin or avidin (Nilsson et al., 1997), and CBDs which binds specifically to cellulose (Linder et al., 1998; Tomme et al., 1998). Oriented immobilization of a protein may also be achieved by using immobilized antibodies that binds the protein or through carbohydrate moieties that may be present on the protein surface (Turkova, 1999).

[0036] Recently, amine oxidase from pea seedlings was immobilized using a modified carbon paste to yield a biosensor for determination of biogenic and synthetic amines (Wimmerova and Macholan, 1999). Similarly, recombinant human SSAO might be immobilized for construction of biosensors to detect e.g. the cardiovascular toxin allylamine which is used in industrial organic processes and is a substrate for SSAO (Boor and Hysmith, 1987; Conklin et al., 1998). When immobilized, recombinant SSAO may be envisioned to mimic a membrane-anchored SSAO and its characteristics, which might differ from the soluble state.

[0037] Consequently, as shown in the following examples, the invention provides a procedure for the production of a highly purified soluble recombinant human SSAO with enzymatic activity. The exemplified procedure involves the use of a mutant form of S. japonicum glutathione S-transferase (GST), designed for transport out of the host cells (Tudyka and Skerra, 1997), as an affinity fusion partner. The fusion protein was secreted from mammalian cells and could be purified directly from the culture medium by glutathione-affinity chromatography. By specific proteolysis and an additional glutathione-affinity chromatography step, the fusion partner and the protease were removed, whereby pure, soluble and highly active recombinant human SSAO protein was obtained in milligram quantities. To the inventors' knowledge, this is the first time an active recombinant soluble form of the human SSAO protein has been produced and purified to near homogeneity.

[0038] It is believed that the disclosed process for production of recombinant human SSAO will be applicable also to other mammalian amine oxidases, such as the human placenta diamine oxidase (Zhang et al., 1995) and the human retina-specific amine oxidase (Imamura et al., 1998), as well as for other secretable proteins. The disclosed process may also facilitate the discovery and identification of modifications e.g. the identification of the active site cofactor, e.g. by isolation of cofactor-containing peptides or by crystal structure determination.

[0039] In the following examples, it is shown that SSAO is active and soluble without its transmembrane region, and that GST can be proteolytically removed. These findings support the hypothesis that SSAO is released into circulation by proteolytic cleavage near the transmembrane region (shedding), a process which is common for Type I and Type II membrane proteins (Hooper et al., 1997). The elevated SSAO activity in plasma in e.g. diabetes (Boomsma et al., 1999) may thus be the consequence of increased proteolytic activity of a protease that cleave the membrane-anchored SSAO, or of increased surface localization increasing the substrate availability for an existing protease.

[0040] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Suitable methods and materials are described below, although methods and materials similar or equivalent to those described herein can also be used in the practice or testing of the present invention. All publications, patent applications, patents, and other references mentioned herein are incorporated by reference in their entirety. In case of conflict, the present specification, including definitions, will control. In addition, the materials, methods, and examples are illustrative only and not intended to be limiting.

[0041] Other features and advantages of the invention will be apparent from the following detailed description, and from the claims.

EXPERIMENTAL METHODS

[0042] PCR-amplification and Cloning of the Human SSAO Gene from Aorta cDNA

[0043] Two PCR-primers were designed with the help of the published cDNA sequence of human placenta amine oxidase (GenBank Accession No. U39447; Zhang and McIntire, 1996). The 5′-primer XNQZ-15 (5′-CCG GAA TTC CAA CGC GTC CAT GAA CCA GAA GAC AAT CCT CGT G-3′; SEQ ID NO: 7) was designed to hybridize to the 5′-end of the SSAO coding sequence including the ATG start codon and to contain the restriction enzyme cleavage sites EcoRI and MluI for cloning. The 3′-primer XNQZ-17 (5′-CCC CCA AGC TTG TCG ACT CAC TAG TTG TGA GAG AGA AGC CCC CCC-3′; SEQ ID NO: 8) was designed to hybridize to the 3′-end including the native stop codon TAG followed by an additional stop codon TGA and two restriction enzyme cleavage sites for cloning, SalI and HindIII. As template for the PCR 0.5 μl human aorta or human smooth muscle cell QUICK-Clone cDNAs (1 ng/μl, Clontech Laboratories, Palo Alto, Calif.) were tested. The following conditions was used for the PCR-reaction, 20 pmol of each primer XNQX-15 and XNQZ-17, 1 μl dNTPs (10 mM), 1 μl Advantage cDNA Polymerase Mix (Clontech), 5 μl 10×cDNA PCR reaction buffer (Clontech) in a total volume of 50 μl. Amplification was performed with a Perkin-Elmer 2400 thermocycler (Perkin-Elmer, Norwalk, Conn.). The PCR-program consisted of an initial denaturation at 94° C. for 5 min, 35 cycles of 94° C. for 30 s, 60° C. for 30 s and 72° C. for 3 min followed by a final extension at 72° C. for 3 min. TA-cloning was then used to insert the PCR-product into the vector pCR2. 1-TOPO (Invitrogen, Carlsbad, Calif.). The cloned PCR-fragment was sequenced in both directions according to a standard protocol for dye terminator cycle sequencing and analyzed on a DNA sequencer ABI 377 (Applied Biosystems, Foster City, Calif.).

[0044] Construction of Vectors for Expression of SSAO in Mammalian Cells

[0045] A vector for expression of the complete SSAO protein in mammalian cells was prepared by insertion of the EcoRI and SalI fragment from the pCR2.1 ITOPO-SSAO vector into the same sites of the vector pCI-neo (Promega, Madison, Wis.), resulting in the vector pMB843. This vector was used as template for PCR-amplification of the region corresponding to residues 29-763 of the human SSAO (Zhang and McIntire, 1996). A 5′-primer 5′-GAG GAA GCT TTG TTC CAA GGT GGA GAT GGG GGT GAA-3' (SEQ ID NO: 9) was synthesized containing codons for a partial 3C protease cleavage site (see below) and a HindIII restriction enzyme cleavage site upstream of the codon for residue 29. The 3′-primer 5′-GCA TTC TAG TTG TGG TTT GTC-3' (SEQ ID NO: 10) is a pCI-neo vector specific primer annealing downstream of the cloned SSAO fragment. The resulting PCR-product was digested with HindIII and NotI and cloned into the plasmid pET38b(+) (Novagen, Inc., Madison, Wis.) cut with same enzymes, resulting in pET38-SSAO. DNA sequencing was performed as described above to verify expected sequence of the cloned SSAO fragment.

[0046] A mutated form (SEQ ID NO: 5) of the glutathione S-transferase (GST) from S. japonicum previously used as a secretable enzymatically active dimerization module for a recombinant protein (Tudyka and Skerra, 1997) was prepared by PCR-mediated mutagenesis and assembly of fragments as described below. The mutations was performed to replace three cysteine residues 85, 138, and 178 located close to the GST protein surface as revealed in the crystal structure of the S. japonicum GST (Lim et al., 1994; Tudyka and Skerra, 1997) with serine residues in order to avoid unwanted disulphide formation after export of the GST fusion protein to an oxidizing environment (Tudyka and Skerra, 1997). The following PCR-primers were used to construct the mutated GST and to introduce the first part of a 3C protease cleavage site (see below) as well as suitable restriction enzyme cleavage sites for cloning. In addition, the primers introduce internal restriction sites for control cleavage and for possibility to assemble PCR-fragments by ligation: ROEL-1 (5′-GCC GGA ATT CGA CGC GTC CCC TAT ACT AGG TTA TTG G-3′; SEQ ID NO: 11) contains EcoRI and MluI for cloning and anneals to codons 2-8 of GST (M14654); ROEL-2 (5′-CTC TGC GCG CTC TTT TGG AGA ACC CAA CAT GTT GTG C-3′; SEQ ID NO: 12) contains a BssHII site; ROEL-3 (5′-GGT TCT CCA AAA GAG CGC GCA GAG ATT TCA ATG CTT GAA G-3′; SEQ ID NO: 13) contains a BssHII site; ROEL-4 (5′-ATG AGA TAA ACG GTC TTC GAA CAT TTT CAG CAT TTC-3′; SEQ ID NO: 14) contains a BbsI site; ROEL-5 (5′-GTT CGA AGA CCG TTT ATC TCA TAA AAC ATA TTT AAA TGG TGA TC-3′; SEQ ID NO: 15) contains a BbsI site; ROEL-6 (5′-AAA AGA AAC TAG TTT TGG GAA CGC ATC CAG GCA-3′; SEQ ID NO: 16) contains a Spel site; ROEL-7 (5′-CCC AAA ACT AGT TTC TTT TAA AAA ACG TAT TGA AGC TAT C-3′; SEQ ID NO: 17) contains a Spel site; ROEL-8 (5′-ACC CAA GCT TCC TGA CTT TGT GAC TTT GGA GGA TGG TCG CCA CC-3′; SEQ ID NO: 18) contains HindIII for cloning and anneals to codons 212-218 of GST (M14654). ROEL-8 will also introduce codons for a spacer-sequence SQSQ before a partial 3C protease cleavage site. Overlapping parts of the GST gene were amplified in separate PCR-reactions with primer pairs ROEL-1/2, ROEL-3/4, ROEL-4/5 and ROEL-7/8, using plasmid pGEX-6P-2 (Amersham Pharmacia Biotech) as template. This allowed the complete mutated GST gene to be assembled by mixing the four PCR-fragments and using them as templates in a PCR reaction with primers ROEL-1 and ROEL-8. The PCR-reactions was performed using the Advantage cDNA PCR Kit (Clontech). In the next step the GST fragment was digested with EcoRI and HindIII and cloned into the same sites of pUC 18 (Amersham Pharmacia Biotech), yielding pMB809. DNA sequencing was performed as described above to confirm the expected sequence of the mutated GST fragment. The pMB809 vector was cleaved with EcoRI and HindIII and the GST fragment was isolated and cloned upstream of the SSAO fragment in the pET38-SSAO vector cut with the same enzymes. This step resulted in the creation of a complete 3C protease cleavage site EALFQG (SEQ ID NO: 6) of human rhinovirus-14 and coxsackievirus (Miyashita et al., 1996; Wang et al., 1997) between GST and SSAO (residues 29-763) (see FIG. 1).

[0047] The GST-SSAO fragment was cloned in the MluI and SalI site of the vector pMB565, in which a mutated signal sequence of a murine IgG1 heavy chain (FIG. 1) is cloned in the multilinker of the mammalian expression vector pCI-neo (Promega). The resulting GST-SSAO expression vector was named pMB887 (FIG. 3).

[0048] Transfection and Selection of Stable Clones

[0049] Three 25 cm² T-flasks were seeded with approximately 4×10⁵ human embryo kidney 293 cells (HEK293 cells, ATCC CRL-1573, Rockville, Md.). Cells were grown to ˜50% conflueny in growth medium containing Dulbecco's modified Eagle's medium (DMEM) supplemented with 10% fetal bovine serum (FBS) and 2 mM L-Glutamine. The FBS was heat-inactivated at 56° C. for 30 min before mixed with the growth medium components. The expression vector pMB887 was then introduced into the cells by liposome-mediated transfection using LipofectAMINE according to the manufacturer's recommendations (Life Technologies, Frederick, Md.). After 48 hours of growth the medium was changed in all flasks to growth medium supplemented with 1 mg/ml geneticin (G418) for selection of stably transfected cells. Approximately two weeks later, resistant cells emerged and were grown to confluency. Cells from the three T-flasks were pooled (clone-mixture) and diluted in growth medium supplemented with 1.2 mg/ml G418 and seeded in a 15-cm Petri dish. Individual colonies emerged after two weeks and were picked to be expanded individually for subsequent analysis of GST-SSAO production. Detection of GST proteins in collected medium from expanded clones was performed using the GST 96-Well Detection Module (Amersham Pharmacia Biotech). Seven positive clones were selected and frozen.

[0050] Production of GST-SSAO in Cell Factories

[0051] Clone number 10 was expanded and cultured in growth medium containing DMEM supplemented with 5% FBS (heat-inactivated), 2 mM L-Glutamine and 1.2 mg/ml G418 and used to seed a 6320 cm²Nunc Cell Factory (Nalge Nunc Int., Naperville, Ill.) containing 1500 ml of growth medium and grown at 37° C. After four days of growth, cells were confluent and medium was collected. New growth medium (1500 ml) with reduced amount of FBS (2%) was then added to the cells in the same Cell Factory followed by harvest of conditioned medium after three days. This procedure was repeated once resulting in a total of ˜4.5 liters of harvested medium from one Cell Factory. Collected medium was centrifuged and stored at −70° C.

[0052] Concentration of Conditioned Cell Medium

[0053] Frozen conditioned medium from two Cell Factories (9.4 liters) was thawed in a water-bath at 30° C. The material was pumped through an Omega membrane (MWCO (Molecular-Weight Cut-Off) 10000) using a Centramate ultra-filtration equipment (Pall Filtron, Northborough, Mass.), until a volume of 600 ml was achieved. The retentate was filtered through a 0.45 μm filter, Sartobran P, equipped with a 0.65 μm prefilter (Sartorius, Göttingen, Germany). Remaining filtrate in tubings was displaced by 250 ml of phosphate-buffered saline (PBS) yielding 850 ml of filtered sample.

[0054] Purification and Cleavage of GST-SSAO

[0055] The GST-SSAO fusion protein was purified by glutathione-affinity chromatography on a HR 10/10 column (Amersham Pharmacia Biotech) packed with 8 ml glutathione-Sepharose 4 Fast Flow (Binds˜10 mg GST/ml gel, Amersham Pharmacia Biotech), equilibrated with 10 column volumes of PBS. The filtered material (850 ml), was loaded at 0.9 ml/min over night at room temperature. Flow-through material was collected for analysis and stored at −20° C. After washing the column with PBS, bound proteins were eluted with elution buffer (20 mM GSH, 0.1 M NaCl, 0.1 M Tris-HCl, pH 8.2).

[0056] The eluate was loaded on a HiPrep Desalt 26/10 column (Amersham Pharmacia Biotech) equilibrated with helium-sparged cleavage-buffer (150 mM NaCl, 1 mM EDTA, 50 mM Tris-HCl, pH 7.5 at 25° C.) and the protein peak was collected. Cleavage was started by adding DTT (dithiothreitol) to 5 mM and 380 units of PreScission protease (Amersham Pharmacia Biotech). The PreScission Protease is a genetically engineered fusion protein consisting of GST and human rhinovirus 3C protease and cleaves specifically between the Gln (Q) and Gly (G) residues of its recognition sequence.

[0057] The cleavage mixture was incubated at 5° C. After 63 hours of incubation the material was loaded on a glutathione-Sepharose column as described above, equilibrated with cleavage buffer. The flow-through (36 ml) was collected and stored at 5° C. for approximately one week in an open tube. Samples were withdrawn and analyzed by SDS-PAGE (non-reducing). Proteins captured on the column were eluted with elution buffer for analysis. The collected protein sample was applied on a JumboSep device (MWCO 30000, Pall Filtron) for buffer exchange and concentration. Fiva cycles of centrifugation and dilution with a buffer containing 50 mM Tris-HCl (pH 7.5) and 150 mM NaCl were performed. A sample was taken for different analyses. The buffer exchanged and concentrated material (4.2 ml) was then stored at −70° C.

[0058] Protein Analyses

[0059] The purification and size of SSAO were analyzed by SDS-PAGE. Samples were electrophoresed in the presence or absence of 2-mercaptoethanol in gradient gels 4-20% or 4-12% (Novex, Copenhagen, Denmark) and proteins were visualized by Coomassie staining (PhastGel Blue R, Amersham Pharmacia Biotech). Protein concentrations were determined with Coomassie Plus protein assay reagent kit (Pierce, Rockford, Ill.) in 96-well plates with bovine serum albumin as standard according to the manufacturer's procedure.

[0060] Size exclusion chromatography was performed on a Superdex 200 PC 3.2/30 column (Amersham Pharmacia Biotech) using the SMART System (Amersham Pharmacia Biotech). The column was equilibrated at room temperature with a buffer containing 50 mM Tris-HCl (pH 7.5), 150 mM NaCl and 1 mM EDTA. Injection volume was 10 μl and samples were eluted at a flow rate of 0.1 ml/min. For column calibration molecular weight markers Blue Dextran 2000 (˜2000 kDa), thyroglobulin (669 kDa), ferritin (440 kDa), catalase (232 kDa) and aldolase (158 kDa) from the Gel Filtration HMW Calibration Kit (Amersham Pharmacia Biotech) was used.

[0061] N-terminal sequencing was performed on purified GST-SSAO and SSAO by repeated Edman degradation using a HP G1000A protein sequencer coupled to a HP 1090 PTH analyzer (Hewlett Packard, Palo Alto, Calif.). The GST-SSAO sample was desalted to remove glutathione prior to analysis. SSAO was taken from the flow-through of the glutathione-Sepharose column after cleavage.

[0062] A spectrophotometric assay for monoamine oxidases described by Holt and coworkers (Holt et al., 1997) was used to determine amine oxidase activity in samples from the different purification steps. The assay was performed in 96-well microtiter plates incubated at 37° C. in a SPECTRAmax 250 microplate spectrophotometer (Molecular Devices, Sunnyvale, Calif.). The reagent mix containing 1 mM vanillic acid (Sigma, St. Louis, Mo.), 500 μM 4-aminoantipyrine (Sigma), and 4U ml⁻¹ peroxidase (type VI from horseradish, Sigma) in 0.2 M potassium phosphate buffer (pH 7.6) was prepared on the same day assays were performed and kept at 5° C. until used. Reactions were started by mixing 50 μl sample, 50 μl reagent mix and 200 μl potassium phosphate buffer with or without 750 μM benzylamine hydrochloride (Sigma) and were performed in triplicate. In order to obtain blank reference values, wells were analyzed with buffer added in place of sample. Absorbance changes were followed at 490 nm for 10-40 minutes. Standard curves were prepared with dilutions of a stock solution of H₂O₂ in potassium phosphate buffer ranging from 10 nmol/well to 120 nmol/well. When inhibition experiments were carried out, the samples were incubated in 300 μM semicarbazide at 37° C. for 30 minutes, before addition of the benzylamine solution.

[0063] The invention will now be described with reference to the following examples. These are only intended to exemplify the invention and are not to be considered as limiting the scope of the invention in any way.

EXAMPLES Example 1

[0064] Cloning of SSAO cDNA

[0065] A PCR-strategy was used to amplify the gene of a human SSAO from human aorta cDNA. The PCR-primers were designed to include sequences flanking the human placenta amine oxidase gene (Zhang and McIntire, 1996) and to include restriction enzyme cleavage sites for cloning into different expression vectors. The ˜2300 bp PCR-product was cloned and subsequent DNA-sequencing showed that the sequence of the cloned PCR-product was identical to the human placenta amine oxidase sequence (Zhang and McIntire, 1996) and to the VAP-1 sequence cloned from lung cDNA (Smith et al., 1998).

Example 2 Purification of Membrane-bound SSAO (Example for Comparison)

[0066] Attempts to produce a recombinant SSAO protein showed that active SSAO could be produced in human embryo kidney (HEK293) cells using the pMB843 vector in which the entire coding sequence of human SSAO was cloned. Active protein was found after extraction using solubilizing agents, but only microgram amounts of protein could be partially purified.

Example 3

[0067] Rationale and Design of a Gene Construct for Expression of a Soluble Form of SSAO

[0068] An alternative strategy was developed for production of a non-membrane-bound SSAO in mammalian cells. Purification and detection were performed by replacing the N-terminal region containing the putative membrane spanning peptide with an affinity fusion partner having an inherent dimerization propensity. The strategy also involved the use of a secretable affinity fusion partner to be able to secrete the fusion protein into the culture medium. A mutated variant of S. japonicum glutathione S-transferase (GST) was selected. This mutant GST retains its activity as well as its propensity to dimerize and have been optimized for secretion (Tudyka and Skerra, 1997).

[0069] A protease cleavage site was designed to enable release of SSAO from the purified GST-SSAO fusion protein. Scanning of the predicted amino acid sequence revealed an arginine at position 28 flanked by three glycine residues. Several human proteases cleave after basic residues (Carter, 1990; Hooper et al., 1997) and short stretches of glycine residues have been suggested to enhance accessibility to proteases (Carter, 1990). In addition, the proteolytic release of the extracellular region (shedding) of many membrane-anchored proteins into the blood stream occurs close to the membrane (Hooper et al., 1997). The glycine residue at position 29 was therefore chosen to be linked to a suitable substrate for site-specific proteolysis after purification of the GST-SSAO fusion protein. Thus, a protease that can cleave a substrate having a glycine in the P1' position and having high specificity was desired. Several commercial proteases exist having these two properties such as factor Xa, thrombin, enterokinase and 3C protease (Nilsson et al., 1997). The ability to easily capture the protease after cleavage was another factor considered, leading to the selection of a commercially available 3C protease fused to GST. The 3C protease cleavage site EALFQG (SEQ ID NO: 6) (Miyashita et al., 1996; Wang et al., 1997) was introduced in the GST-SSAO fusion construct (FIG. 1).

[0070] The GST-SSAO fragment was cloned in frame with a signal sequence to achieve secretion of the GST-SSAO fusion protein into the culture medium. A signal sequence derived from the heavy chain of a murine antibody was used (see FIG. 1). The final construct thus encoded a fusion protein comprising of an antibody signal peptide, an 18 amino acid spacer region, the mutated GST protein, a substrate sequence for the 3C protease and residues 29-763 of the human SSAO protein cloned from human aorta cDNA (FIG. 1). The calculated molecular weight of the unmodified GST-SSAO fusion protein is 112 kDa.

Example 4

[0071] Initial Analyses on Conditioned Medium from HEK293 Cells Transfected with the GST-SSAO Expression Vector

[0072] Benzylamine oxidase activity in the conditioned medium from small-scale cultures of HEK293 cells, stably transfected with the GST-SSAO expression vector pMB887, indicated that GST-SSAO was secreted into the culture medium. Further analyses showed that glutathione-Sepharose beads could be used to purify small amounts of the GST-SSAO fusion protein directly from the conditioned medium (data not shown), and that the purified material had benzylamine oxidase activity. Interestingly, the GST-SSAO fusion protein was found to be active also when immobilized on the glutathione Sepharose beads. The amount of GST-SSAO fusion protein in the conditioned medium was calculated to be ˜1 mg/l, by estimation of the amount of protein captured on the beads.

Example 5

[0073] Preparative Purification and Site-specific Cleavage of the GST-SSAO Fusion Protein

[0074] An overview of the affinity purification based procedure is shown in FIG. 2. The results of the purification are summarized in Table 1. One selected clone was expanded and grown in Cell Factories to generate larger amounts of GST-SSAO for purification. The harvested conditioned medium were concentrated and filtrated to reduce the time for loading on the glutathione-Sepharose column. Glutathione-affinity chromatography was then applied to purify the GST-SSAO fusion protein from the concentrated and filtered conditioned medium. Proteins captured on the column were eluted with 20 mM GSH and analyzed by SDS-PAGE under reducing conditions. This showed that the GST-SSAO fusion protein had high purity and that it could be isolated from large amounts of other proteins in the culture medium in a single step. The GST-SSAO fusion protein migrated in level with the 116 kDa protein in the molecular weight marker. In total 8.8 mg of protein was recovered from the glutathione-Sepharose column. The specific activity of the GST-SSAO fusion protein was determined to 343 nmol·min⁻¹·mg⁻¹. Interestingly, the specific activity was almost doubled (634 nmol·min⁻¹·mg⁻¹) by the buffer exchange step which removed the reducing agent GSH.

[0075] The glutathione-affinity purified GST-SSAO was cleaved with the GST-3C protease fusion protein (46 kDa) to remove the GST fusion partner from SSAO. Analytical experiments suggested that cleavage was slow, but precise, with no observable side-products. Moreover, complete cleavage could be obtained after ˜48 hours incubation. The cleavage mixture was passed over the glutathione-Sepharose column to capture the removed GST fusion partner and the GST-3C protease. Flow-through material was collected and analyzed by SDS-PAGE under reducing conditions which showed only the expected SSAO product with a molecular weight of ˜97 kDa. Captured material was also analyzed, which showed only the GST fusion partner (˜28 kDa) and the GST-3C protease. This indicated that a complete cleavage had occurred and all GST containing proteins had been captured on the glutathione-Sepharose column. It also indicated that all SSAO protein had passed through the column since no SSAO protein was seen in the eluted material.

[0076] The specific activity of the purified SSAO protein was determined to 522 nmol·min⁻¹·mg⁻¹ which was less than the specific activity determined before cleavage. Since DTT had been used to ensure 3C protease activity during cleavage of the GST-SSAO fusion protein, we made an SDS-PAGE analysis (non-reducing) to see if the cleavage buffer had affected possible disulphide bridges in the SSAO homodimer (Kurkijärvi et al., 1998; Smith et al., 1998; Salminen et al., 1998). Only presumed SSAO monomers (˜97 kDa) could be seen (data not shown). However, the SSAO protein was transformed to ˜170 kDa in size (analyzed by SDS-PAGE) during storage at 5° C., indicating that one or several disulphides were formed. The cleavage buffer was removed by diafiltration and SDS-PAGE analysis showed that the SSAO protein was still apparently dimeric with a molecular weight of ˜170 kDa. In total 3.6 mg of recombinant SSAO was obtained from 9.4 liters of conditioned medium having a specific activity of 809 nmol·min⁻¹·mg⁻¹. The overall yield in the process was 22% based on determined benzylamine oxidase activity.

[0077] Interestingly, the GST fusion partner did not significantly affect the benzylamine oxidase activity of the SSAO protein. The specific activity of the purified GST-SSAO fusion protein after the buffer exchange step, was determined to 634 nmol·min⁻¹·mg⁻¹. After removal of the GST fusion partner, the specific activity of SSAO was determined to 809 nmol·min⁻¹·mg⁻¹. However, the molecular mass of the GST fusion partner is ˜25% of the GST-SSAO fusion protein and the increase in specific activity after removal of GST was in the same range. This opens up possibilities to use the fusion protein for enzyme characterization. Furthermore, an affinity fusion partner such as GST can be used to bind or immobilize a recombinant protein in a directed manner on solid supports to study e.g. protein-protein interactions and enzyme characteristics (Nilsson et al., 1997). The GST-SSAO fusion protein was indeed active when it was bound to glutathione-Sepharose beads.

Example 6 Initial Characterization of Purified SSAO Proteins

[0078] A gel filtration experiment was performed to analyze the size of the SSAO protein under non-denaturing conditions. A sample from the SSAO protein material that migrated as a dimeric protein when investigated by SDS-PAGE under non-reducing conditions was loaded on a calibrated analytical Superdex 200 column. The SSAO protein eluted at 1.29 ml, which was slightly faster than catalase (232 kDa), which eluted at 1.35 ml.

[0079] N-terminal amino acid sequencing of the purified SSAO protein showed that the GST-3C protease had specifically cleaved the 3C protease substrate sequence EALFQG (SEQ ID NO: 6) in the GST-SSAO fusion protein (FIG. 1). Twenty-nine amino acids were determined and corresponded exactly to residues number 29-58 in the predicted SSAO amino acid sequence (SEQ ID NO: 2). N-terminal sequencing was also performed on the GST-SSAO fusion protein, which showed that the signal peptide had been processed as anticipated.

[0080] Finally, the purified SSAO protein was found to be sensitive to inhibition by semicarbazide as expected. In the presence of 0.1 mM semicarbazide more than 95% of the benzylamine oxidase activity was inhibited. TABLE I Purification of recombinant human SSAO Purification step Total volume Total protein Total SSAO activity^(a) Specific activity Yield (sample) (ml) (mg) (nmol min⁻¹) (nmol min⁻¹ mg⁻¹) (%) Conditioned medium 9400 9024 9243   1.0 — Concentrated medium 600 9060 13200    1.5 100  Filtrate 850 9065 11900    1.3 90 GSH-affinity step-1 (eluate) 6.8 8.8 3029 343  23 Buffer exchange 15 8.9  5624^(b) 634^(b )  43 GSH-affinity step-2 (flow-through)^(c) 36 5.5 2859 522  22 Diafiltrate^(d) 4.2 3.6 2919 809  22

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[0140] Zhang, X and McIntire, W. S. (1996) Cloning and sequencing of a copper-containing, topa quinone-containing monoamine oxidase from human placenta. Gene 179, 279-286.

1 20 1 4040 DNA Homo sapiens CDS (161)...(2449) 1 gtccttccca cccttagtcc caggcatctg actaccggga acctcagcca gagtccggga 60 gccccccacc ccgtccagga gccaacagag cccccgtctt gctggcgtga gaatacattg 120 ctctcctttg gttgaatcag ctgtccctct tcgtgggaaa atg aac cag aag aca 175 Met Asn Gln Lys Thr 1 5 atc ctc gtg ctc ctc att ctg gcc gtc atc acc atc ttt gcc ttg gtt 223 Ile Leu Val Leu Leu Ile Leu Ala Val Ile Thr Ile Phe Ala Leu Val 10 15 20 tgt gtc ctg ctg gtg ggc agg ggt gga gat ggg ggt gaa ccc agc cag 271 Cys Val Leu Leu Val Gly Arg Gly Gly Asp Gly Gly Glu Pro Ser Gln 25 30 35 ctt ccc cat tgc ccc tct gta tct ccc agt gcc cag cct tgg aca cac 319 Leu Pro His Cys Pro Ser Val Ser Pro Ser Ala Gln Pro Trp Thr His 40 45 50 cct ggc cag agc cag ctg ttt gca gac ctg agc cga gag gag ctg acg 367 Pro Gly Gln Ser Gln Leu Phe Ala Asp Leu Ser Arg Glu Glu Leu Thr 55 60 65 gct gtg atg cgc ttt ctg acc cag cgg ctg ggg cca ggg ctg gtg gat 415 Ala Val Met Arg Phe Leu Thr Gln Arg Leu Gly Pro Gly Leu Val Asp 70 75 80 85 gca gcc cag gcc cgg ccc tcg gac aac tgt gtc ttc tca gtg gag ttg 463 Ala Ala Gln Ala Arg Pro Ser Asp Asn Cys Val Phe Ser Val Glu Leu 90 95 100 cag ctg cct ccc aag gct gca gcc ctg gct cac ttg gac agg ggg agc 511 Gln Leu Pro Pro Lys Ala Ala Ala Leu Ala His Leu Asp Arg Gly Ser 105 110 115 ccc cca cct gcc cgg gag gca ctg gcc atc gtc ttc ttt ggc agg caa 559 Pro Pro Pro Ala Arg Glu Ala Leu Ala Ile Val Phe Phe Gly Arg Gln 120 125 130 ccc cag ccc aac gtg agt gag ctg gtg gtg ggg cca ctg cct cac ccc 607 Pro Gln Pro Asn Val Ser Glu Leu Val Val Gly Pro Leu Pro His Pro 135 140 145 tcc tac atg cgg gac gtg act gtg gag cgt cat gga ggc ccc ctg ccc 655 Ser Tyr Met Arg Asp Val Thr Val Glu Arg His Gly Gly Pro Leu Pro 150 155 160 165 tat cac cga cgc ccc gtg ctg ttc caa gag tac ctg gac ata gac cag 703 Tyr His Arg Arg Pro Val Leu Phe Gln Glu Tyr Leu Asp Ile Asp Gln 170 175 180 atg atc ttc aac aga gag ctg ccc cag gct tct ggg ctt ctc cac cac 751 Met Ile Phe Asn Arg Glu Leu Pro Gln Ala Ser Gly Leu Leu His His 185 190 195 tgt tgc ttc tac aag cac cgg gga cgg aac ctg gtg aca atg acc acg 799 Cys Cys Phe Tyr Lys His Arg Gly Arg Asn Leu Val Thr Met Thr Thr 200 205 210 gct ccc cgt ggt ctg caa tca ggg gac cgg gcc acc tgg ttt ggc ctc 847 Ala Pro Arg Gly Leu Gln Ser Gly Asp Arg Ala Thr Trp Phe Gly Leu 215 220 225 tac tac aac atc tcg ggc gct ggg ttc ttc ctg cac cac gtg ggc ttg 895 Tyr Tyr Asn Ile Ser Gly Ala Gly Phe Phe Leu His His Val Gly Leu 230 235 240 245 gag ctg cta gtg aac cac aag gcc ctt gac cct gcc cgc tgg act atc 943 Glu Leu Leu Val Asn His Lys Ala Leu Asp Pro Ala Arg Trp Thr Ile 250 255 260 cag aag gtg ttc tat caa ggc cgc tac tac gac agc ctg gcc cag ctg 991 Gln Lys Val Phe Tyr Gln Gly Arg Tyr Tyr Asp Ser Leu Ala Gln Leu 265 270 275 gag gcc cag ttt gag gcc ggc ctg gtg aat gtg gtg ctg atc cca gac 1039 Glu Ala Gln Phe Glu Ala Gly Leu Val Asn Val Val Leu Ile Pro Asp 280 285 290 aat ggc aca ggt ggg tcc tgg tcc ctg aag tcc cct gtg ccc ccg ggt 1087 Asn Gly Thr Gly Gly Ser Trp Ser Leu Lys Ser Pro Val Pro Pro Gly 295 300 305 cca gct ccc cct cta cag ttc tat ccc caa ggc ccc cgc ttc agt gtc 1135 Pro Ala Pro Pro Leu Gln Phe Tyr Pro Gln Gly Pro Arg Phe Ser Val 310 315 320 325 cag gga agt cga gtg gcc tcc tca ctg tgg act ttc tcc ttt ggc ctc 1183 Gln Gly Ser Arg Val Ala Ser Ser Leu Trp Thr Phe Ser Phe Gly Leu 330 335 340 gga gca ttc agt ggc cca agg atc ttt gac gtt cgc ttc caa gga gaa 1231 Gly Ala Phe Ser Gly Pro Arg Ile Phe Asp Val Arg Phe Gln Gly Glu 345 350 355 aga cta gtt tat gag ata agc ctc caa gag gcc ttg gcc atc tat ggt 1279 Arg Leu Val Tyr Glu Ile Ser Leu Gln Glu Ala Leu Ala Ile Tyr Gly 360 365 370 gga aat tcc cca gca gca atg acg acc cgc tat gtg gat gga ggc ttt 1327 Gly Asn Ser Pro Ala Ala Met Thr Thr Arg Tyr Val Asp Gly Gly Phe 375 380 385 ggc atg ggc aag tac acc acg ccc ctg acc cgt ggg gtg gac tgc ccc 1375 Gly Met Gly Lys Tyr Thr Thr Pro Leu Thr Arg Gly Val Asp Cys Pro 390 395 400 405 tac ttg gcc acc tac gtg gac tgg cac ttc ctt ttg gag tcc cag gcc 1423 Tyr Leu Ala Thr Tyr Val Asp Trp His Phe Leu Leu Glu Ser Gln Ala 410 415 420 ccc aag aca ata cgt gat gcc ttt tgt gtg ttt gaa cag aac cag ggc 1471 Pro Lys Thr Ile Arg Asp Ala Phe Cys Val Phe Glu Gln Asn Gln Gly 425 430 435 ctc ccc ctg cgg cga cac cac tca gat ctc tac tcg cac tac ttt ggg 1519 Leu Pro Leu Arg Arg His His Ser Asp Leu Tyr Ser His Tyr Phe Gly 440 445 450 ggt ctt gcg gaa acg gtg ctg gtc gtc aga tct atg tcc acc ttg ctc 1567 Gly Leu Ala Glu Thr Val Leu Val Val Arg Ser Met Ser Thr Leu Leu 455 460 465 aac tat gac tat gtg tgg gat acg gtc ttc cac ccc agt ggg gcc ata 1615 Asn Tyr Asp Tyr Val Trp Asp Thr Val Phe His Pro Ser Gly Ala Ile 470 475 480 485 gaa ata cga ttc tat gcc acg ggc tac atc agc tcg gca ttc ctc ttt 1663 Glu Ile Arg Phe Tyr Ala Thr Gly Tyr Ile Ser Ser Ala Phe Leu Phe 490 495 500 ggt gct act ggg aag tac ggg aac caa gtg tca gag cac acc ctg ggc 1711 Gly Ala Thr Gly Lys Tyr Gly Asn Gln Val Ser Glu His Thr Leu Gly 505 510 515 acg gtc cac acc cac agc gcc cac ttc aag gtg gat ctg gat gta gca 1759 Thr Val His Thr His Ser Ala His Phe Lys Val Asp Leu Asp Val Ala 520 525 530 gga ctg gag aac tgg gtc tgg gcc gag gat atg gtc ttt gtc ccc atg 1807 Gly Leu Glu Asn Trp Val Trp Ala Glu Asp Met Val Phe Val Pro Met 535 540 545 gct gtg ccc tgg agc cct gag cac cag ctg cag agg ctg cag gtg acc 1855 Ala Val Pro Trp Ser Pro Glu His Gln Leu Gln Arg Leu Gln Val Thr 550 555 560 565 cgg aag ctg ctg gag atg gag gag cag gcc gcc ttc ctc gtg gga agc 1903 Arg Lys Leu Leu Glu Met Glu Glu Gln Ala Ala Phe Leu Val Gly Ser 570 575 580 gcc acc cct cgc tac ctg tac ctg gcc agc aac cac agc aac aag tgg 1951 Ala Thr Pro Arg Tyr Leu Tyr Leu Ala Ser Asn His Ser Asn Lys Trp 585 590 595 ggt cac ccc cgg ggc tac cgc atc cag atg ctc agc ttt gct gga gag 1999 Gly His Pro Arg Gly Tyr Arg Ile Gln Met Leu Ser Phe Ala Gly Glu 600 605 610 ccg ctg ccc caa aac agc tcc atg gcg aga ggc ttc agc tgg gag agg 2047 Pro Leu Pro Gln Asn Ser Ser Met Ala Arg Gly Phe Ser Trp Glu Arg 615 620 625 tac cag ctg gct gtg acc cag cgg aag gag gag gag ccc agt agc agc 2095 Tyr Gln Leu Ala Val Thr Gln Arg Lys Glu Glu Glu Pro Ser Ser Ser 630 635 640 645 agc gtt ttc aat cag aat gac cct tgg gcc ccc act gtg gat ttc agt 2143 Ser Val Phe Asn Gln Asn Asp Pro Trp Ala Pro Thr Val Asp Phe Ser 650 655 660 gac ttc atc aac aat gag acc att gct gga aag gat ttg gtg gcc tgg 2191 Asp Phe Ile Asn Asn Glu Thr Ile Ala Gly Lys Asp Leu Val Ala Trp 665 670 675 gtg aca gct ggt ttt ctg cat atc cca cat gca gag gac att cct aac 2239 Val Thr Ala Gly Phe Leu His Ile Pro His Ala Glu Asp Ile Pro Asn 680 685 690 aca gtg act gtg ggg aac ggc gtg ggc ttc ttc ctc cga ccc tat aac 2287 Thr Val Thr Val Gly Asn Gly Val Gly Phe Phe Leu Arg Pro Tyr Asn 695 700 705 ttc ttt gac gaa gac ccc tcc ttc tac tct gcc gac tcc atc tac ttc 2335 Phe Phe Asp Glu Asp Pro Ser Phe Tyr Ser Ala Asp Ser Ile Tyr Phe 710 715 720 725 cga ggg gac cag gat gct ggg gcc tgc gag gtc aac ccc cta gct tgc 2383 Arg Gly Asp Gln Asp Ala Gly Ala Cys Glu Val Asn Pro Leu Ala Cys 730 735 740 ctg ccc cag gct gct gcc tgt gcc ccc gac ctc cct gcc ttc tcc cac 2431 Leu Pro Gln Ala Ala Ala Cys Ala Pro Asp Leu Pro Ala Phe Ser His 745 750 755 ggg ggc ttc tct cac aac taggcggtcc tgggatgggg catgtggcca 2479 Gly Gly Phe Ser His Asn 760 agggctccag ggccagggtg tgagggatgg ggagcagctg ggcactgggc cggcagcctg 2539 gttccctctt tcctgtgcca ggactctctt tcttccacta ccctccctcg catccgcctc 2599 tgagccagga gcctcctgac cctgtgatgc ctgacacagg ggacactgaa ccttgttgat 2659 gccagctgta ctgagttctc atccacagag gccaggcatg gcccagcctg gagccgtggc 2719 cgagggcttc cctagatggt tccctttgtt gctgtctggc tttcccgaat ctttttaggc 2779 cacctccaag gactctaaaa gggggctatt ccctggagac cccagagtag ggttgccagt 2839 cctgcaagtc catagctgag ctggaaagga tgcttctgct cacattccct ctcatccagg 2899 tcctttcctt ctcgtcttcc tctctctcac ctacttcctc ctcctcctcc tgttcctgcc 2959 ttctcttcta tcctgcaatt tctcccgaat cctgagggga tatccctatg tcccagcccc 3019 tggtactccc ccagccctca gttttcagtc aagttccgtc tcctctccag ccctatggaa 3079 gtctcaaggt cacgggaccc ctaatcagag tggccaatcc ctgtgtgtcg ttcccttgtg 3139 tctgttgctt attgggagta ggagttgctc ctacccctgt cctggggctg ggtgtgtttc 3199 aggacagctg cttctgtgca tttgtgtctg cctgcctcat gctctctata gaggaggatg 3259 gtcatcgtga cagcagcagc tcaagttagc atttcaagtg atttgggggt gcaatgataa 3319 tgaagaatgg ccattttgta ccagggctct gtattctgca acagcctgtt tgggaggctg 3379 gagtggaaac aaagggtggg catcaaagat gagaagccaa agcccctaca actccagcca 3439 cccagccagg aggggctgtc caatcacatt caggcatgcg aatgagctgg gccctgggtg 3499 aggtgggggt ctggcctagt ggggaggggc ctggcctggg tggggcaggg cctggcctgg 3559 tccaggcttg ggctccattc ccatcactgc tgtccctcct gaggtctgga ttggggatgg 3619 ggacaaagaa atagcaagag atgagaaaca acagaaactt ttttctctaa aggactggtt 3679 aaatcaattc tgatacagcc ttacaataca atagtatgca gctaaaaaat aattgtatgt 3739 ctttatatac taatatgtaa taatcttcag gtgaaaaagg caagccacag aaatgtgtat 3799 agcgcacttc ccatttgtgt ttcagaaagg agtagaatat aaacacataa ttgcttatgt 3859 atgcctattc agaataaatg ggtaacactg attacttttg ggaggggaac cagtaggttg 3919 aggacaggag agggaagggt cttaacactt acaccctttt gtacattttg aattttgaac 3979 catgtgactg tattacctat tcaaaataaa caataaatgg gcccaaaaaa aaaaaaaaaa 4039 a 4040 2 763 PRT Homo sapiens 2 Met Asn Gln Lys Thr Ile Leu Val Leu Leu Ile Leu Ala Val Ile Thr 1 5 10 15 Ile Phe Ala Leu Val Cys Val Leu Leu Val Gly Arg Gly Gly Asp Gly 20 25 30 Gly Glu Pro Ser Gln Leu Pro His Cys Pro Ser Val Ser Pro Ser Ala 35 40 45 Gln Pro Trp Thr His Pro Gly Gln Ser Gln Leu Phe Ala Asp Leu Ser 50 55 60 Arg Glu Glu Leu Thr Ala Val Met Arg Phe Leu Thr Gln Arg Leu Gly 65 70 75 80 Pro Gly Leu Val Asp Ala Ala Gln Ala Arg Pro Ser Asp Asn Cys Val 85 90 95 Phe Ser Val Glu Leu Gln Leu Pro Pro Lys Ala Ala Ala Leu Ala His 100 105 110 Leu Asp Arg Gly Ser Pro Pro Pro Ala Arg Glu Ala Leu Ala Ile Val 115 120 125 Phe Phe Gly Arg Gln Pro Gln Pro Asn Val Ser Glu Leu Val Val Gly 130 135 140 Pro Leu Pro His Pro Ser Tyr Met Arg Asp Val Thr Val Glu Arg His 145 150 155 160 Gly Gly Pro Leu Pro Tyr His Arg Arg Pro Val Leu Phe Gln Glu Tyr 165 170 175 Leu Asp Ile Asp Gln Met Ile Phe Asn Arg Glu Leu Pro Gln Ala Ser 180 185 190 Gly Leu Leu His His Cys Cys Phe Tyr Lys His Arg Gly Arg Asn Leu 195 200 205 Val Thr Met Thr Thr Ala Pro Arg Gly Leu Gln Ser Gly Asp Arg Ala 210 215 220 Thr Trp Phe Gly Leu Tyr Tyr Asn Ile Ser Gly Ala Gly Phe Phe Leu 225 230 235 240 His His Val Gly Leu Glu Leu Leu Val Asn His Lys Ala Leu Asp Pro 245 250 255 Ala Arg Trp Thr Ile Gln Lys Val Phe Tyr Gln Gly Arg Tyr Tyr Asp 260 265 270 Ser Leu Ala Gln Leu Glu Ala Gln Phe Glu Ala Gly Leu Val Asn Val 275 280 285 Val Leu Ile Pro Asp Asn Gly Thr Gly Gly Ser Trp Ser Leu Lys Ser 290 295 300 Pro Val Pro Pro Gly Pro Ala Pro Pro Leu Gln Phe Tyr Pro Gln Gly 305 310 315 320 Pro Arg Phe Ser Val Gln Gly Ser Arg Val Ala Ser Ser Leu Trp Thr 325 330 335 Phe Ser Phe Gly Leu Gly Ala Phe Ser Gly Pro Arg Ile Phe Asp Val 340 345 350 Arg Phe Gln Gly Glu Arg Leu Val Tyr Glu Ile Ser Leu Gln Glu Ala 355 360 365 Leu Ala Ile Tyr Gly Gly Asn Ser Pro Ala Ala Met Thr Thr Arg Tyr 370 375 380 Val Asp Gly Gly Phe Gly Met Gly Lys Tyr Thr Thr Pro Leu Thr Arg 385 390 395 400 Gly Val Asp Cys Pro Tyr Leu Ala Thr Tyr Val Asp Trp His Phe Leu 405 410 415 Leu Glu Ser Gln Ala Pro Lys Thr Ile Arg Asp Ala Phe Cys Val Phe 420 425 430 Glu Gln Asn Gln Gly Leu Pro Leu Arg Arg His His Ser Asp Leu Tyr 435 440 445 Ser His Tyr Phe Gly Gly Leu Ala Glu Thr Val Leu Val Val Arg Ser 450 455 460 Met Ser Thr Leu Leu Asn Tyr Asp Tyr Val Trp Asp Thr Val Phe His 465 470 475 480 Pro Ser Gly Ala Ile Glu Ile Arg Phe Tyr Ala Thr Gly Tyr Ile Ser 485 490 495 Ser Ala Phe Leu Phe Gly Ala Thr Gly Lys Tyr Gly Asn Gln Val Ser 500 505 510 Glu His Thr Leu Gly Thr Val His Thr His Ser Ala His Phe Lys Val 515 520 525 Asp Leu Asp Val Ala Gly Leu Glu Asn Trp Val Trp Ala Glu Asp Met 530 535 540 Val Phe Val Pro Met Ala Val Pro Trp Ser Pro Glu His Gln Leu Gln 545 550 555 560 Arg Leu Gln Val Thr Arg Lys Leu Leu Glu Met Glu Glu Gln Ala Ala 565 570 575 Phe Leu Val Gly Ser Ala Thr Pro Arg Tyr Leu Tyr Leu Ala Ser Asn 580 585 590 His Ser Asn Lys Trp Gly His Pro Arg Gly Tyr Arg Ile Gln Met Leu 595 600 605 Ser Phe Ala Gly Glu Pro Leu Pro Gln Asn Ser Ser Met Ala Arg Gly 610 615 620 Phe Ser Trp Glu Arg Tyr Gln Leu Ala Val Thr Gln Arg Lys Glu Glu 625 630 635 640 Glu Pro Ser Ser Ser Ser Val Phe Asn Gln Asn Asp Pro Trp Ala Pro 645 650 655 Thr Val Asp Phe Ser Asp Phe Ile Asn Asn Glu Thr Ile Ala Gly Lys 660 665 670 Asp Leu Val Ala Trp Val Thr Ala Gly Phe Leu His Ile Pro His Ala 675 680 685 Glu Asp Ile Pro Asn Thr Val Thr Val Gly Asn Gly Val Gly Phe Phe 690 695 700 Leu Arg Pro Tyr Asn Phe Phe Asp Glu Asp Pro Ser Phe Tyr Ser Ala 705 710 715 720 Asp Ser Ile Tyr Phe Arg Gly Asp Gln Asp Ala Gly Ala Cys Glu Val 725 730 735 Asn Pro Leu Ala Cys Leu Pro Gln Ala Ala Ala Cys Ala Pro Asp Leu 740 745 750 Pro Ala Phe Ser His Gly Gly Phe Ser His Asn 755 760 3 739 DNA Schistosoma japonicum CDS (17)...(670) 3 tttaggtaac ttggtc atg tcc cct ata cta ggt tat tgg aaa att aag ggc 52 Met Ser Pro Ile Leu Gly Tyr Trp Lys Ile Lys Gly 1 5 10 ctt gtg caa ccc act cga ctt ctt ttg gaa tat ctt gaa gaa aaa tat 100 Leu Val Gln Pro Thr Arg Leu Leu Leu Glu Tyr Leu Glu Glu Lys Tyr 15 20 25 gaa gag cat ttg tat gag cgc gat gaa ggt gat aaa tgg cga aac aaa 148 Glu Glu His Leu Tyr Glu Arg Asp Glu Gly Asp Lys Trp Arg Asn Lys 30 35 40 aag ttt gaa ttg ggt ttg gag ttt ccc aat ctt cct tat tat att gat 196 Lys Phe Glu Leu Gly Leu Glu Phe Pro Asn Leu Pro Tyr Tyr Ile Asp 45 50 55 60 ggt gat gtt aaa tta aca cag tct atg gcc atc ata cgt tat ata gct 244 Gly Asp Val Lys Leu Thr Gln Ser Met Ala Ile Ile Arg Tyr Ile Ala 65 70 75 gac aag cac aac atg ttg ggt ggt tgt cca aaa gag cgt gca gag att 292 Asp Lys His Asn Met Leu Gly Gly Cys Pro Lys Glu Arg Ala Glu Ile 80 85 90 tca atg ctt gaa gga gcg gtt ttg gat att aga tac ggt gtt tcg aga 340 Ser Met Leu Glu Gly Ala Val Leu Asp Ile Arg Tyr Gly Val Ser Arg 95 100 105 att gca tat agt aaa gac ttt gaa act ctc aaa gtt gat ttt ctt agc 388 Ile Ala Tyr Ser Lys Asp Phe Glu Thr Leu Lys Val Asp Phe Leu Ser 110 115 120 aag cta cct gaa atg ctg aaa atg ttc gaa gat cgt tta tgt cat aaa 436 Lys Leu Pro Glu Met Leu Lys Met Phe Glu Asp Arg Leu Cys His Lys 125 130 135 140 aca tat tta aat ggt gat cat gta acc cat cct gac ttc atg ttg tat 484 Thr Tyr Leu Asn Gly Asp His Val Thr His Pro Asp Phe Met Leu Tyr 145 150 155 gac gct ctt gat gtt gtt tta tac atg gac cca atg tgc ctg gat gcg 532 Asp Ala Leu Asp Val Val Leu Tyr Met Asp Pro Met Cys Leu Asp Ala 160 165 170 ttc cca aaa tta gtt tgt ttt aaa aaa cgt att gaa gct atc cca caa 580 Phe Pro Lys Leu Val Cys Phe Lys Lys Arg Ile Glu Ala Ile Pro Gln 175 180 185 att gat aag tac ttg aaa tcc agc aag tat ata gca tgg cct ttg cag 628 Ile Asp Lys Tyr Leu Lys Ser Ser Lys Tyr Ile Ala Trp Pro Leu Gln 190 195 200 ggc tgg caa gcc acg ttt ggt ggt ggc gac cat cct cca aaa 670 Gly Trp Gln Ala Thr Phe Gly Gly Gly Asp His Pro Pro Lys 205 210 215 taaattaaga atgattgttt tagtaaacat tatttatcac ttacaattaa actaaatata 730 aatgtcgac 739 4 218 PRT Schistosoma japonicum 4 Met Ser Pro Ile Leu Gly Tyr Trp Lys Ile Lys Gly Leu Val Gln Pro 1 5 10 15 Thr Arg Leu Leu Leu Glu Tyr Leu Glu Glu Lys Tyr Glu Glu His Leu 20 25 30 Tyr Glu Arg Asp Glu Gly Asp Lys Trp Arg Asn Lys Lys Phe Glu Leu 35 40 45 Gly Leu Glu Phe Pro Asn Leu Pro Tyr Tyr Ile Asp Gly Asp Val Lys 50 55 60 Leu Thr Gln Ser Met Ala Ile Ile Arg Tyr Ile Ala Asp Lys His Asn 65 70 75 80 Met Leu Gly Gly Cys Pro Lys Glu Arg Ala Glu Ile Ser Met Leu Glu 85 90 95 Gly Ala Val Leu Asp Ile Arg Tyr Gly Val Ser Arg Ile Ala Tyr Ser 100 105 110 Lys Asp Phe Glu Thr Leu Lys Val Asp Phe Leu Ser Lys Leu Pro Glu 115 120 125 Met Leu Lys Met Phe Glu Asp Arg Leu Cys His Lys Thr Tyr Leu Asn 130 135 140 Gly Asp His Val Thr His Pro Asp Phe Met Leu Tyr Asp Ala Leu Asp 145 150 155 160 Val Val Leu Tyr Met Asp Pro Met Cys Leu Asp Ala Phe Pro Lys Leu 165 170 175 Val Cys Phe Lys Lys Arg Ile Glu Ala Ile Pro Gln Ile Asp Lys Tyr 180 185 190 Leu Lys Ser Ser Lys Tyr Ile Ala Trp Pro Leu Gln Gly Trp Gln Ala 195 200 205 Thr Phe Gly Gly Gly Asp His Pro Pro Lys 210 215 5 218 PRT Schistosoma japonicum 5 Met Ser Pro Ile Leu Gly Tyr Trp Lys Ile Lys Gly Leu Val Gln Pro 1 5 10 15 Thr Arg Leu Leu Leu Glu Tyr Leu Glu Glu Lys Tyr Glu Glu His Leu 20 25 30 Tyr Glu Arg Asp Glu Gly Asp Lys Trp Arg Asn Lys Lys Phe Glu Leu 35 40 45 Gly Leu Glu Phe Pro Asn Leu Pro Tyr Tyr Ile Asp Gly Asp Val Lys 50 55 60 Leu Thr Gln Ser Met Ala Ile Ile Arg Tyr Ile Ala Asp Lys His Asn 65 70 75 80 Met Leu Gly Gly Ser Pro Lys Glu Arg Ala Glu Ile Ser Met Leu Glu 85 90 95 Gly Ala Val Leu Asp Ile Arg Tyr Gly Val Ser Arg Ile Ala Tyr Ser 100 105 110 Lys Asp Phe Glu Thr Leu Lys Val Asp Phe Leu Ser Lys Leu Pro Glu 115 120 125 Met Leu Lys Met Phe Glu Asp Arg Leu Ser His Lys Thr Tyr Leu Asn 130 135 140 Gly Asp His Val Thr His Pro Asp Phe Met Leu Tyr Asp Ala Leu Asp 145 150 155 160 Val Val Leu Tyr Met Asp Pro Met Cys Leu Asp Ala Phe Pro Lys Leu 165 170 175 Val Ser Phe Lys Lys Arg Ile Glu Ala Ile Pro Gln Ile Asp Lys Tyr 180 185 190 Leu Lys Ser Ser Lys Tyr Ile Ala Trp Pro Leu Gln Gly Trp Gln Ala 195 200 205 Thr Phe Gly Gly Gly Asp His Pro Pro Lys 210 215 6 6 PRT Artificial Sequence Protease cleavage site 6 Glu Ala Leu Phe Gln Gly 1 5 7 43 DNA Artificial Sequence PCR primer 7 ccggaattcc aacgcgtcca tgaaccagaa gacaatcctc gtg 43 8 45 DNA Artificial Sequence PCR primer 8 cccccaagct tgtcgactca ctagttgtga gagagaagcc ccccc 45 9 36 DNA Artificial Sequence PCR primer 9 gaggaagctt tgttccaagg tggagatggg ggtgaa 36 10 21 DNA Artificial Sequence PCR primer 10 gcattctagt tgtggtttgt c 21 11 37 DNA Artificial Sequence PCR primer 11 gccggaattc gacgcgtccc ctatactagg ttattgg 37 12 37 DNA Artificial Sequence PCR primer 12 ctctgcgcgc tcttttggag aacccaacat gttgtgc 37 13 40 DNA Artificial Sequence PCR primer 13 ggttctccaa aagagcgcgc agagatttca atgcttgaag 40 14 36 DNA Artificial Sequence PCR primer 14 atgagataaa cggtcttcga acattttcag catttc 36 15 44 DNA Artificial Sequence PCR primer 15 gttcgaagac cgtttatctc ataaaacata tttaaatggt gatc 44 16 33 DNA Artificial Sequence PCR primer 16 aaaagaaact agttttggga acgcatccag gca 33 17 40 DNA Artificial Sequence PCR primer 17 cccaaaacta gtttctttta aaaaacgtat tgaagctatc 40 18 44 DNA Artificial Sequence PCR primer 18 acccaagctt cctgactttg tgactttgga ggatggtcgc cacc 44 19 3006 DNA Artificial Sequence Recombinant construct 19 atg gat tgg ctg cgg aac ttg cta ttc ctg atg gcg gcc gct caa agt 48 Met Asp Trp Leu Arg Asn Leu Leu Phe Leu Met Ala Ala Ala Gln Ser 1 5 10 15 atc aac gcc gcg caa cac gat gaa gcc gta gac aac aaa ttc aac aaa 96 Ile Asn Ala Ala Gln His Asp Glu Ala Val Asp Asn Lys Phe Asn Lys 20 25 30 gaa caa caa aac gcg tcc cct ata cta ggt tat tgg aaa att aag ggc 144 Glu Gln Gln Asn Ala Ser Pro Ile Leu Gly Tyr Trp Lys Ile Lys Gly 35 40 45 ctt gtg caa ccc act cga ctt ctt ttg gaa tat ctt gaa gaa aaa tat 192 Leu Val Gln Pro Thr Arg Leu Leu Leu Glu Tyr Leu Glu Glu Lys Tyr 50 55 60 gaa gag cat ttg tat gag cgc gat gaa ggt gat aaa tgg cga aac aaa 240 Glu Glu His Leu Tyr Glu Arg Asp Glu Gly Asp Lys Trp Arg Asn Lys 65 70 75 80 aag ttt gaa ttg ggt ttg gag ttt ccc aat ctt cct tat tat att gat 288 Lys Phe Glu Leu Gly Leu Glu Phe Pro Asn Leu Pro Tyr Tyr Ile Asp 85 90 95 ggt gat gtt aaa tta aca cag tct atg gcc atc ata cgt tat ata gct 336 Gly Asp Val Lys Leu Thr Gln Ser Met Ala Ile Ile Arg Tyr Ile Ala 100 105 110 gac aag cac aac atg ttg ggt ggt tct cca aaa gag cgc gca gag att 384 Asp Lys His Asn Met Leu Gly Gly Ser Pro Lys Glu Arg Ala Glu Ile 115 120 125 tca atg ctt gaa gga gcg gtt ttg gat att aga tac ggt gtt tcg aga 432 Ser Met Leu Glu Gly Ala Val Leu Asp Ile Arg Tyr Gly Val Ser Arg 130 135 140 att gca tat agt aaa gac ttt gaa act ctc aaa gtt gat ttt ctt agc 480 Ile Ala Tyr Ser Lys Asp Phe Glu Thr Leu Lys Val Asp Phe Leu Ser 145 150 155 160 aag cta cct gaa atg ctg aaa atg ttc gaa gac cgt tta tct cat aaa 528 Lys Leu Pro Glu Met Leu Lys Met Phe Glu Asp Arg Leu Ser His Lys 165 170 175 aca tat tta aat ggt gat cat gta acc cat cct gac ttc atg ttg tat 576 Thr Tyr Leu Asn Gly Asp His Val Thr His Pro Asp Phe Met Leu Tyr 180 185 190 gac gct ctt gat gtt gtt tta tac atg gac cca atg tgc ctg gat gcg 624 Asp Ala Leu Asp Val Val Leu Tyr Met Asp Pro Met Cys Leu Asp Ala 195 200 205 ttc cca aaa cta gtt tct ttt aaa aaa cgt att gaa gct atc cca caa 672 Phe Pro Lys Leu Val Ser Phe Lys Lys Arg Ile Glu Ala Ile Pro Gln 210 215 220 att gat aag tac ttg aaa tcc agc aag tat ata gca tgg cct ttg cag 720 Ile Asp Lys Tyr Leu Lys Ser Ser Lys Tyr Ile Ala Trp Pro Leu Gln 225 230 235 240 ggc tgg caa gcc acg ttt ggt ggt ggc gac cat cct cca aag tca caa 768 Gly Trp Gln Ala Thr Phe Gly Gly Gly Asp His Pro Pro Lys Ser Gln 245 250 255 agt cag gaa gct ttg ttc caa ggt gga gat ggg ggt gaa ccc agc cag 816 Ser Gln Glu Ala Leu Phe Gln Gly Gly Asp Gly Gly Glu Pro Ser Gln 260 265 270 ctt ccc cat tgc ccc tct gta tct ccc agt gcc cag cct tgg aca cac 864 Leu Pro His Cys Pro Ser Val Ser Pro Ser Ala Gln Pro Trp Thr His 275 280 285 cct ggc cag agc cag ctg ttt gca gac ctg agc cga gag gag ctg acg 912 Pro Gly Gln Ser Gln Leu Phe Ala Asp Leu Ser Arg Glu Glu Leu Thr 290 295 300 gct gtg atg cgc ttt ctg acc cag cgg ctg ggg cca ggg ctg gtg gat 960 Ala Val Met Arg Phe Leu Thr Gln Arg Leu Gly Pro Gly Leu Val Asp 305 310 315 320 gca gcc cag gcc cgg ccc tcg gac aac tgt gtc ttc tca gtg gag ttg 1008 Ala Ala Gln Ala Arg Pro Ser Asp Asn Cys Val Phe Ser Val Glu Leu 325 330 335 cag ctg cct ccc aag gct gca gcc ctg gct cac ttg gac agg ggg agc 1056 Gln Leu Pro Pro Lys Ala Ala Ala Leu Ala His Leu Asp Arg Gly Ser 340 345 350 ccc cca cct gcc cgg gag gca ctg gcc atc gtc ttc ttt ggc agg caa 1104 Pro Pro Pro Ala Arg Glu Ala Leu Ala Ile Val Phe Phe Gly Arg Gln 355 360 365 ccc cag ccc aac gtg agt gag ctg gtg gtg ggg cca ctg cct cac ccc 1152 Pro Gln Pro Asn Val Ser Glu Leu Val Val Gly Pro Leu Pro His Pro 370 375 380 tcc tac atg cgg gac gtg act gtg gag cgt cat gga ggc ccc ctg ccc 1200 Ser Tyr Met Arg Asp Val Thr Val Glu Arg His Gly Gly Pro Leu Pro 385 390 395 400 tat cac cga cgc ccc gtg ctg ttc caa gag tac ctg gac ata gac cag 1248 Tyr His Arg Arg Pro Val Leu Phe Gln Glu Tyr Leu Asp Ile Asp Gln 405 410 415 atg atc ttc aac aga gag ctg ccc cag gct tct ggg ctt ctc cac cac 1296 Met Ile Phe Asn Arg Glu Leu Pro Gln Ala Ser Gly Leu Leu His His 420 425 430 tgt tgc ttc tac aag cac cgg gga cgg aac ctg gtg aca atg acc acg 1344 Cys Cys Phe Tyr Lys His Arg Gly Arg Asn Leu Val Thr Met Thr Thr 435 440 445 gct ccc cgt ggt ctg caa tca ggg gac cgg gcc acc tgg ttt ggc ctc 1392 Ala Pro Arg Gly Leu Gln Ser Gly Asp Arg Ala Thr Trp Phe Gly Leu 450 455 460 tac tac aac atc tcg ggc gct ggg ttc ttc ctg cac cac gtg ggc ttg 1440 Tyr Tyr Asn Ile Ser Gly Ala Gly Phe Phe Leu His His Val Gly Leu 465 470 475 480 gag ctg cta gtg aac cac aag gcc ctt gac cct gcc cgc tgg act atc 1488 Glu Leu Leu Val Asn His Lys Ala Leu Asp Pro Ala Arg Trp Thr Ile 485 490 495 cag aag gtg ttc tat caa ggc cgc tac tac gac agc ctg gcc cag ctg 1536 Gln Lys Val Phe Tyr Gln Gly Arg Tyr Tyr Asp Ser Leu Ala Gln Leu 500 505 510 gag gcc cag ttt gag gcc ggc ctg gtg aat gtg gtg ctg atc cca gac 1584 Glu Ala Gln Phe Glu Ala Gly Leu Val Asn Val Val Leu Ile Pro Asp 515 520 525 aat ggc aca ggt ggg tcc tgg tcc ctg aag tcc cct gtg ccc ccg ggt 1632 Asn Gly Thr Gly Gly Ser Trp Ser Leu Lys Ser Pro Val Pro Pro Gly 530 535 540 cca gct ccc cct cta cag ttc tat ccc caa ggc ccc cgc ttc agt gtc 1680 Pro Ala Pro Pro Leu Gln Phe Tyr Pro Gln Gly Pro Arg Phe Ser Val 545 550 555 560 cag gga agt cga gtg gcc tcc tca ctg tgg act ttc tcc ttt ggc ctc 1728 Gln Gly Ser Arg Val Ala Ser Ser Leu Trp Thr Phe Ser Phe Gly Leu 565 570 575 gga gca ttc agt ggc cca agg atc ttt gac gtt cgc ttc caa gga gaa 1776 Gly Ala Phe Ser Gly Pro Arg Ile Phe Asp Val Arg Phe Gln Gly Glu 580 585 590 aga cta gtt tat gag ata agc ctc caa gag gcc ttg gcc atc tat ggt 1824 Arg Leu Val Tyr Glu Ile Ser Leu Gln Glu Ala Leu Ala Ile Tyr Gly 595 600 605 gga aat tcc cca gca gca atg acg acc cgc tat gtg gat gga ggc ttt 1872 Gly Asn Ser Pro Ala Ala Met Thr Thr Arg Tyr Val Asp Gly Gly Phe 610 615 620 ggc atg ggc aag tac acc acg ccc ctg acc cgt ggg gtg gac tgc ccc 1920 Gly Met Gly Lys Tyr Thr Thr Pro Leu Thr Arg Gly Val Asp Cys Pro 625 630 635 640 tac ttg gcc acc tac gtg gac tgg cac ttc ctt ttg gag tcc cag gcc 1968 Tyr Leu Ala Thr Tyr Val Asp Trp His Phe Leu Leu Glu Ser Gln Ala 645 650 655 ccc aag aca ata cgt gat gcc ttt tgt gtg ttt gaa cag aac cag ggc 2016 Pro Lys Thr Ile Arg Asp Ala Phe Cys Val Phe Glu Gln Asn Gln Gly 660 665 670 ctc ccc ctg cgg cga cac cac tca gat ctc tac tcg cac tac ttt ggg 2064 Leu Pro Leu Arg Arg His His Ser Asp Leu Tyr Ser His Tyr Phe Gly 675 680 685 ggt ctt gcg gaa acg gtg ctg gtc gtc aga tct atg tcc acc ttg ctc 2112 Gly Leu Ala Glu Thr Val Leu Val Val Arg Ser Met Ser Thr Leu Leu 690 695 700 aac tat gac tat gtg tgg gat acg gtc ttc cac ccc agt ggg gcc ata 2160 Asn Tyr Asp Tyr Val Trp Asp Thr Val Phe His Pro Ser Gly Ala Ile 705 710 715 720 gaa ata cga ttc tat gcc acg ggc tac atc agc tcg gca ttc ctc ttt 2208 Glu Ile Arg Phe Tyr Ala Thr Gly Tyr Ile Ser Ser Ala Phe Leu Phe 725 730 735 ggt gct act ggg aag tac ggg aac caa gtg tca gag cac acc ctg ggc 2256 Gly Ala Thr Gly Lys Tyr Gly Asn Gln Val Ser Glu His Thr Leu Gly 740 745 750 acg gtc cac acc cac agc gcc cac ttc aag gtg gat ctg gat gta gca 2304 Thr Val His Thr His Ser Ala His Phe Lys Val Asp Leu Asp Val Ala 755 760 765 gga ctg gag aac tgg gtc tgg gcc gag gat atg gtc ttt gtc ccc atg 2352 Gly Leu Glu Asn Trp Val Trp Ala Glu Asp Met Val Phe Val Pro Met 770 775 780 gct gtg ccc tgg agc cct gag cac cag ctg cag agg ctg cag gtg acc 2400 Ala Val Pro Trp Ser Pro Glu His Gln Leu Gln Arg Leu Gln Val Thr 785 790 795 800 cgg aag ctg ctg gag atg gag gag cag gcc gcc ttc ctc gtg gga agc 2448 Arg Lys Leu Leu Glu Met Glu Glu Gln Ala Ala Phe Leu Val Gly Ser 805 810 815 gcc acc cct cgc tac ctg tac ctg gcc agc aac cac agc aac aag tgg 2496 Ala Thr Pro Arg Tyr Leu Tyr Leu Ala Ser Asn His Ser Asn Lys Trp 820 825 830 ggt cac ccc cgg ggc tac cgc atc cag atg ctc agc ttt gct gga gag 2544 Gly His Pro Arg Gly Tyr Arg Ile Gln Met Leu Ser Phe Ala Gly Glu 835 840 845 ccg ctg ccc caa aac agc tcc atg gcg aga ggc ttc agc tgg gag agg 2592 Pro Leu Pro Gln Asn Ser Ser Met Ala Arg Gly Phe Ser Trp Glu Arg 850 855 860 tac cag ctg gct gtg acc cag cgg aag gag gag gag ccc agt agc agc 2640 Tyr Gln Leu Ala Val Thr Gln Arg Lys Glu Glu Glu Pro Ser Ser Ser 865 870 875 880 agc gtt ttc aat cag aat gac cct tgg gcc ccc act gtg gat ttc agt 2688 Ser Val Phe Asn Gln Asn Asp Pro Trp Ala Pro Thr Val Asp Phe Ser 885 890 895 gac ttc atc aac aat gag acc att gct gga aag gat ttg gtg gcc tgg 2736 Asp Phe Ile Asn Asn Glu Thr Ile Ala Gly Lys Asp Leu Val Ala Trp 900 905 910 gtg aca gct ggt ttt ctg cat atc cca cat gca gag gac att cct aac 2784 Val Thr Ala Gly Phe Leu His Ile Pro His Ala Glu Asp Ile Pro Asn 915 920 925 aca gtg act gtg ggg aac ggc gtg ggc ttc ttc ctc cga ccc tat aac 2832 Thr Val Thr Val Gly Asn Gly Val Gly Phe Phe Leu Arg Pro Tyr Asn 930 935 940 ttc ttt gac gaa gac ccc tcc ttc tac tct gcc gac tcc atc tac ttc 2880 Phe Phe Asp Glu Asp Pro Ser Phe Tyr Ser Ala Asp Ser Ile Tyr Phe 945 950 955 960 cga ggg gac cag gat gct ggg gcc tgc gag gtc aac ccc cta gct tgc 2928 Arg Gly Asp Gln Asp Ala Gly Ala Cys Glu Val Asn Pro Leu Ala Cys 965 970 975 ctg ccc cag gct gct gcc tgt gcc ccc gac ctc cct gcc ttc tcc cac 2976 Leu Pro Gln Ala Ala Ala Cys Ala Pro Asp Leu Pro Ala Phe Ser His 980 985 990 ggg ggc ttc tct cac aac tagtgagtcg ac 3006 Gly Gly Phe Ser His Asn 995 20 998 PRT Artificial Sequence Recombinant construct 20 Met Asp Trp Leu Arg Asn Leu Leu Phe Leu Met Ala Ala Ala Gln Ser 1 5 10 15 Ile Asn Ala Ala Gln His Asp Glu Ala Val Asp Asn Lys Phe Asn Lys 20 25 30 Glu Gln Gln Asn Ala Ser Pro Ile Leu Gly Tyr Trp Lys Ile Lys Gly 35 40 45 Leu Val Gln Pro Thr Arg Leu Leu Leu Glu Tyr Leu Glu Glu Lys Tyr 50 55 60 Glu Glu His Leu Tyr Glu Arg Asp Glu Gly Asp Lys Trp Arg Asn Lys 65 70 75 80 Lys Phe Glu Leu Gly Leu Glu Phe Pro Asn Leu Pro Tyr Tyr Ile Asp 85 90 95 Gly Asp Val Lys Leu Thr Gln Ser Met Ala Ile Ile Arg Tyr Ile Ala 100 105 110 Asp Lys His Asn Met Leu Gly Gly Ser Pro Lys Glu Arg Ala Glu Ile 115 120 125 Ser Met Leu Glu Gly Ala Val Leu Asp Ile Arg Tyr Gly Val Ser Arg 130 135 140 Ile Ala Tyr Ser Lys Asp Phe Glu Thr Leu Lys Val Asp Phe Leu Ser 145 150 155 160 Lys Leu Pro Glu Met Leu Lys Met Phe Glu Asp Arg Leu Ser His Lys 165 170 175 Thr Tyr Leu Asn Gly Asp His Val Thr His Pro Asp Phe Met Leu Tyr 180 185 190 Asp Ala Leu Asp Val Val Leu Tyr Met Asp Pro Met Cys Leu Asp Ala 195 200 205 Phe Pro Lys Leu Val Ser Phe Lys Lys Arg Ile Glu Ala Ile Pro Gln 210 215 220 Ile Asp Lys Tyr Leu Lys Ser Ser Lys Tyr Ile Ala Trp Pro Leu Gln 225 230 235 240 Gly Trp Gln Ala Thr Phe Gly Gly Gly Asp His Pro Pro Lys Ser Gln 245 250 255 Ser Gln Glu Ala Leu Phe Gln Gly Gly Asp Gly Gly Glu Pro Ser Gln 260 265 270 Leu Pro His Cys Pro Ser Val Ser Pro Ser Ala Gln Pro Trp Thr His 275 280 285 Pro Gly Gln Ser Gln Leu Phe Ala Asp Leu Ser Arg Glu Glu Leu Thr 290 295 300 Ala Val Met Arg Phe Leu Thr Gln Arg Leu Gly Pro Gly Leu Val Asp 305 310 315 320 Ala Ala Gln Ala Arg Pro Ser Asp Asn Cys Val Phe Ser Val Glu Leu 325 330 335 Gln Leu Pro Pro Lys Ala Ala Ala Leu Ala His Leu Asp Arg Gly Ser 340 345 350 Pro Pro Pro Ala Arg Glu Ala Leu Ala Ile Val Phe Phe Gly Arg Gln 355 360 365 Pro Gln Pro Asn Val Ser Glu Leu Val Val Gly Pro Leu Pro His Pro 370 375 380 Ser Tyr Met Arg Asp Val Thr Val Glu Arg His Gly Gly Pro Leu Pro 385 390 395 400 Tyr His Arg Arg Pro Val Leu Phe Gln Glu Tyr Leu Asp Ile Asp Gln 405 410 415 Met Ile Phe Asn Arg Glu Leu Pro Gln Ala Ser Gly Leu Leu His His 420 425 430 Cys Cys Phe Tyr Lys His Arg Gly Arg Asn Leu Val Thr Met Thr Thr 435 440 445 Ala Pro Arg Gly Leu Gln Ser Gly Asp Arg Ala Thr Trp Phe Gly Leu 450 455 460 Tyr Tyr Asn Ile Ser Gly Ala Gly Phe Phe Leu His His Val Gly Leu 465 470 475 480 Glu Leu Leu Val Asn His Lys Ala Leu Asp Pro Ala Arg Trp Thr Ile 485 490 495 Gln Lys Val Phe Tyr Gln Gly Arg Tyr Tyr Asp Ser Leu Ala Gln Leu 500 505 510 Glu Ala Gln Phe Glu Ala Gly Leu Val Asn Val Val Leu Ile Pro Asp 515 520 525 Asn Gly Thr Gly Gly Ser Trp Ser Leu Lys Ser Pro Val Pro Pro Gly 530 535 540 Pro Ala Pro Pro Leu Gln Phe Tyr Pro Gln Gly Pro Arg Phe Ser Val 545 550 555 560 Gln Gly Ser Arg Val Ala Ser Ser Leu Trp Thr Phe Ser Phe Gly Leu 565 570 575 Gly Ala Phe Ser Gly Pro Arg Ile Phe Asp Val Arg Phe Gln Gly Glu 580 585 590 Arg Leu Val Tyr Glu Ile Ser Leu Gln Glu Ala Leu Ala Ile Tyr Gly 595 600 605 Gly Asn Ser Pro Ala Ala Met Thr Thr Arg Tyr Val Asp Gly Gly Phe 610 615 620 Gly Met Gly Lys Tyr Thr Thr Pro Leu Thr Arg Gly Val Asp Cys Pro 625 630 635 640 Tyr Leu Ala Thr Tyr Val Asp Trp His Phe Leu Leu Glu Ser Gln Ala 645 650 655 Pro Lys Thr Ile Arg Asp Ala Phe Cys Val Phe Glu Gln Asn Gln Gly 660 665 670 Leu Pro Leu Arg Arg His His Ser Asp Leu Tyr Ser His Tyr Phe Gly 675 680 685 Gly Leu Ala Glu Thr Val Leu Val Val Arg Ser Met Ser Thr Leu Leu 690 695 700 Asn Tyr Asp Tyr Val Trp Asp Thr Val Phe His Pro Ser Gly Ala Ile 705 710 715 720 Glu Ile Arg Phe Tyr Ala Thr Gly Tyr Ile Ser Ser Ala Phe Leu Phe 725 730 735 Gly Ala Thr Gly Lys Tyr Gly Asn Gln Val Ser Glu His Thr Leu Gly 740 745 750 Thr Val His Thr His Ser Ala His Phe Lys Val Asp Leu Asp Val Ala 755 760 765 Gly Leu Glu Asn Trp Val Trp Ala Glu Asp Met Val Phe Val Pro Met 770 775 780 Ala Val Pro Trp Ser Pro Glu His Gln Leu Gln Arg Leu Gln Val Thr 785 790 795 800 Arg Lys Leu Leu Glu Met Glu Glu Gln Ala Ala Phe Leu Val Gly Ser 805 810 815 Ala Thr Pro Arg Tyr Leu Tyr Leu Ala Ser Asn His Ser Asn Lys Trp 820 825 830 Gly His Pro Arg Gly Tyr Arg Ile Gln Met Leu Ser Phe Ala Gly Glu 835 840 845 Pro Leu Pro Gln Asn Ser Ser Met Ala Arg Gly Phe Ser Trp Glu Arg 850 855 860 Tyr Gln Leu Ala Val Thr Gln Arg Lys Glu Glu Glu Pro Ser Ser Ser 865 870 875 880 Ser Val Phe Asn Gln Asn Asp Pro Trp Ala Pro Thr Val Asp Phe Ser 885 890 895 Asp Phe Ile Asn Asn Glu Thr Ile Ala Gly Lys Asp Leu Val Ala Trp 900 905 910 Val Thr Ala Gly Phe Leu His Ile Pro His Ala Glu Asp Ile Pro Asn 915 920 925 Thr Val Thr Val Gly Asn Gly Val Gly Phe Phe Leu Arg Pro Tyr Asn 930 935 940 Phe Phe Asp Glu Asp Pro Ser Phe Tyr Ser Ala Asp Ser Ile Tyr Phe 945 950 955 960 Arg Gly Asp Gln Asp Ala Gly Ala Cys Glu Val Asn Pro Leu Ala Cys 965 970 975 Leu Pro Gln Ala Ala Ala Cys Ala Pro Asp Leu Pro Ala Phe Ser His 980 985 990 Gly Gly Phe Ser His Asn 995 

What is claimed is:
 1. A nucleic acid comprising a nucleotide sequence encoding a secreted fusion protein comprising: (i) a signal peptide that directs secretion of the fusion protein from a host cell; (ii) a soluble form of human semicarbazide-sensitive amine oxidase (SSAO); (iii) a fusion partner that enables dimerization of the soluble form of human SSAO; and (iv) a protease cleavage site located between the soluble form of human SSAO and the fusion partner.
 2. The nucleic acid according to claim 1, wherein the soluble form of human SSAO comprises amino acids 29 to 763 of SEQ ID NO: 2 or a fragment thereof.
 3. The nucleic acid according to claim 2, wherein the fusion protein has benzylamine oxidase activity.
 4. The nucleic acid according to claim 2, wherein the soluble form of human SSAO comprises amino acids 29 to 763 of SEQ ID NO:
 2. 5. The nucleic acid according to claim 1, wherein the fusion protein lacks the membrane spanning portion of human SSAO.
 6. The nucleic acid according to claim 1, wherein the fusion protein lacks amino acids 6 to 26 of SEQ ID NO:
 2. 7. The nucleic acid according to claim 1, wherein the fusion partner is fused to the N-terminal portion of the soluble form of human SSAO.
 8. The nucleic acid according to claim 1, wherein the fusion partner is glutathione S-transferase or a functionally equivalent variant thereof.
 9. The nucleic acid according to claim 8, wherein the fusion partner is a variant of Schistosoma japonicum glutathione S-transferase, the variant having at least one of the cysteine residues in positions 85, 138, and 178 replaced by another amino acid residue.
 10. The nucleic acid according to claim 8, wherein the fusion partner comprises the amino acid sequence of SEQ ID NO: 4 or SEQ ID NO:
 5. 11. The nucleic acid according to claim 1, wherein the signal peptide is a mouse IgG1 heavy chain signal peptide.
 12. The nucleic acid according to claim 1, wherein the protease cleavage site is a 3C protease cleavage site.
 13. nucleic acid according to claim 12, wherein the 3 C protease cleavage site comprises the amino acid sequence EALFQG (SEQ ID NO: 6).
 14. The nucleic acid according to claim 1, wherein the fusion protein comprises the amino acid sequence of SEQ ID NO:
 20. 15. An expression vector comprising the nucleic acid of claim
 1. 16. An expression vector comprising the nucleic acid of claim
 14. 17. A method for the purification of a recombinant human SSAO, the method comprising: (i) transfecting a cell with the expression vector according to claim 15; (ii) culturing the cell in a culture medium and under conditions wherein the fusion protein encoded by the expression vector is secreted into the culture medium; (iii) binding the secreted fusion protein to a ligand having affinity for the fusion partner; (iv) separating the fusion partner and the soluble form of human SSAO; and (v) recovering the soluble form of human SSAO.
 18. The method according to claim 17, wherein the ligand having affinity for the fusion partner is glutathione or a derivative thereof.
 19. The method according to claim 17, wherein the fusion partner is separated from the soluble form of human SSAO by protease cleavage.
 20. The method according to claim 19, wherein the protease is a picornavirus 3C-protease.
 21. The method according to claim 20, wherein the protease is rhinovirus 3C-protease.
 22. The method according to claim 19, wherein the protease is fused to a fusion partner resulting in a fusion protease.
 23. The method according to claim 22, wherein the fusion protease is separated from the soluble form of human SSAO by a process comprising binding the fusion protease to a ligand having affinity for the fusion protease.
 24. A method for the preparation of an immobilized recombinant human SSAO, the method comprising: (i) transfecting a cell with the expression vector according to claim 15; (ii) culturing the cell in a culture medium and under conditions wherein the fusion protein encoded by the expression vector is secreted into the culture medium; and (iii) binding the secreted fusion protein to a ligand having affinity for the fusion partner to thereby immobilize the fusion protein.
 25. A fusion protein encoded by the nucleic acid of claim
 1. 26. The fusion protein of claim 25, wherein the fusion protein is immobilized on a ligand having affinity for the fusion partner. 